Note: This change is just to start a discussion, not to push it upstream.

Allow netmap to be used on main interface of a port (ccX), i.e.
not only on virtual netmap interface of a port (vccX).

Effects of this change:

• Allow use of ccX interface directly as netmap interface
• vccX is not needeed, one less interface to manage / care about
• Network statistics are reported directly at expected place

Thus, open question for @np: What is the rational / added values of
having a separate netmap interface compared to allow netmap usage on
main interface?

Thanks.